Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$241.74	13.830%	$275.1726	$275.17	$275.15	$275.20
Purchase #2	$67.66	5.432%	$71.3353	$71.34	$71.35	$71.30
Purchase #3	$70.45	4.191%	$73.4026	$73.40	$73.40	$73.40
Purchase #4	$250.56	5.679%	$264.7893	$264.79	$264.80	$264.80
Purchase #5	$127.55	13.115%	$144.2782	$144.28	$144.30	$144.30
Purchase #6	$54.99	7.498%	$59.1132	$59.11	$59.10	$59.10
Purchase #7	$234.95	9.797%	$257.9681	$257.97	$257.95	$258.00
7 purchase totals =	$1,047.90		$1,146.0593	$1,146.06	$1,146.05	$1,146.10